Ti-6Al-4V 합금 표면에 생성된 TiO2 나노튜브의 전석회화 처리
Precalcification Treatment of TiO2 Nanotube on Ti-6Al-4V Alloy
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연구목적: 최근 치과용 임플란트의 임상 경향이 전체 치료기간을 줄일 수 있는 방법에 관심이 집중됨에 따라 불활성의 티타늄 임플란트 표면에 활성을 부여하기 위한 다양한 표면처리 방법이 검토되고 있다. 본 연구에서는 높은 강도가 요구되는 부위의 임플란트 재료로서 사용되고 있지만 표면 특성이 순 티타늄에 비해 떨어지는 Ti-6Al-4V 합금의 골전도성을 개선할 목적으로 시행되었다. 연구 재료 및 방법: 20 × 10 × 2 mm의 Ti-6Al-4V 합금판을 준비한 다음 TiO2 나노튜브를 형성하기 위해DC 정전원 장치의 양극과 음극에 각각 시편과 백금판을 결선하고 0.5 M Na2SO4와 1.0 wt% NaF를 함유하는 전해액을 사용하여 전압 20 V와 전류밀도 30 ㎃/㎠ 조건에서 2시간 동안 양극산화 처리하였다. TiO2 나노튜브 형성 후 산화 피막층의 결정화를 유도하기 위해 600℃에서 2시간 동안 열처리하였고, 표면활성도를 개선하기 위해 0.5 M Na2HPO4 수용액 24시간 침적과 Ca(OH)2 포화 수용액에 5시간 침적을 시행하였다. 준비한 시편의 표면 반응성을 조사하기 위해 pH와 무기이온의 농도를 사람의 혈장과 유사하게 조절한 Hanks 용액 (H2387, Sigma Chemical Co., USA)에 2주간 침적하였다. 결과: 20 V에서의 양극산화처리로 직경 48.0 - 65.0 ㎚ 범위의 무정형의 TiO2 나노튜브가 전체 표면에 걸쳐서 균일하게 생성되는 양상을 보였다. TiO2 나노튜브는 600℃에서 2시간 열처리 후 상대적으로 강한 anatase 피크와 함께 rutile 피크가 관찰되었다. TiO2 나노튜브의 표면활성도는 0.5 M Na2HPO4 수용액 24시간 침적과 Ca(OH)2 포화수용액에 5시간 침적으로 개선되었다. 열처리와 전석회화 처리 후 SBF에 침적한 결과, TiO2 rutile 피크의 상대적 강도는 크게 증가되었지만HA의 석출은 저하되는 경향을 보였다. 결론: 이상의 결과로 미루어 볼 때, 양극산화 처리한 TiO2 나노튜브는 600℃에서의 열처리에 의해 피막층이 안정화되고, 0.5 M Na2HPO4 수용액 24시간 침적과 Ca(OH)2 포화수용액에 5시간 침적으로 표면에 인산칼슘층을 형성하는 것이 표면활성도를 개선하는데 유효함을 알 수 있었다.
Abstract
Statement of problem: Recently precalcification treatment has been studied to shorten the period of the implant. Purpose: This study was performed to evaluate the effect of precalcification treatment of TiO2 Nanotube formed on Ti-6Al-4V Alloy. Material and methods: Specimens of 20 × 10 × 2 mm in dimensions were polished sequentially from #220 to #1000 SiC paper, ultrasonically washed with acetone and distilled water for 5 min, and dried in an oven at 50℃ for 24 hours. The nanotubular layer was processed by electrochemical anodic oxidation in electrolytes containing 0.5 M Na2SO4 and 1.0 wt% NaF. Anodization was carried out using a regulated DC power supply (Kwangduck FA, Korea) at a potential of 20 V and current density of 30 ㎃/㎠ for 2 hours. Specimens were heat-treated at 600℃ for 2 hours to crystallize the amorphous TiO2 nanotubes, and precalcified by soaking in Na2HPO4 solution for 24 hours and then in saturated Ca(OH)2 solution for 5 hours. To evaluate the bioactivity of the precalcified TiO2 nanotube layer, hydroxyapatite formation was investigated in a Hanks’balanced salts solution with pH 7.4 at 36.5℃ for 2 weeks. Results: Vertically oriented amorphous TiO2 nanotubes of diameters 48.0 - 65.0 ㎚ were fabricated by anodizing treatment at 20 V for 2 hours in an 0.5 M Na2SO4 and 1.0 NaF solution. TiO2 nanotubes were composed with strong anatase peak with presence of rutile peak after heat treatment at 600℃. The surface reactivity of TiO2 nanotubes in SBF solution was enhanced by precalcification treatment in 0.5 M Na2HPO4 solution for 24 hours and then in saturated Ca(OH)2 solution for 5 hours. The immersion in Hank’s solution for 2 weeks showed that the intensity of TiO2 rutile peak increased but the surface reactivity decreased by heat treatment at 600℃. Conclusion: This study shows that the precalcified treatment of TiO2 Nanotube formed on Ti-6Al-4V Alloy enhances the surface reactivity.
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